I chose to deduct my turbo tax fees from my federal refund, and i didn't realize it cost 40$ extra to do that. now i want to undo that, but cant

Have you already efiled, and was your return accepted?  If not, we may be able to tell you how to remove it and pay upfront by credit/debit card or a prepaid debit card you can buy in a store.

Thanks for your response! But I figured it out right after I submitted this question. I had to go ahead with payment and choose credit card but not pay, and go back to verify the 40$ charge was taken out, before I actually paid.

You're welcome.  I'm going to leave an Answer anyway to finish this thread, since it may help someone else.

If you chose the option to pay the TurboTax fees out of the Federal refund, there is an additional 39.99 service fee (44.99 for California filers, where it is bundled with Premium Services.)

You can remove that option prior to filing and avoid that service fee, then you can pay the TurboTax fees upfront with credit/debit card or a prepaid debit card you can purchase in a store.

Here's how to remove it and pay upfront, depending on your location:

Filers in states except California:
https://ttlc.intuit.com/questions/1900517-how-do-i-remove-the-refund-processing-service

California filers (where that refund processing option is part of "Premium Services.")
https://ttlc.intuit.com/questions/2154391-how-do-i-remove-the-premium-services-fee